Well drilling process and apparatus



Dec. 27, 1960 L. J. KINNEY WELL DRILLING PROCESS AND APPARATUS 2 Sheets-Sheet 1 Filed NOV. 23, 1956 ,wriliL i QN N I WWI/V701? [1am JAM/5 y fgw United States Patent O WELL DRELING PROCESS AND APPARATUS Lloyd J. Kinney, Whittier, Calif., assignor to Union Oil Company of California, Los Angeles, Calif., a corporation of California Filed Nov. 23, 1956, Ser. No. 624,147

7 Claims. (Cl. 175--5) This invention relates to an improved process and apparatus for rotary drilling of well bores into the earths subsurface, and particularly relates to the drilling of such bores in which an improved control over the weight on the rotary bit is permitted. One very advantageous application of the present invention lies in the drilling of well bores in submerged land masses from floating barges and l the like and conducting other underwater operations whereby the disadvantages caused by tidal and wave action are overcome.

One problem encountered in drilling well bores, as in the production of gas and oil Wells and the like, involves the control or the weight exerted by the drill pipe against the rotary bit which is pressed against the bottom of the well bore. This weight is generated by the weight of drill tubing and the drill collar having a relatively large diameter and Wall thickness which is located immediately above the rotary bit. Part of the total weight of this drill string is supported at the surface by means of suitable hoisting equipment. This is a type of static hoisting in which the object supported is generally stationary, only part of its weight is supported by the hoist, and the supporting force is subject to change with time due to external interfering factors. As the bore deepens and additional stands of drill tubin are added to the drill string, the total weight of tubing obviously rises. Here this added or changing weight is the interfering factor. In order to maintain a relatively constant weight on the bit, the fraction which is supported from the surface must be increased and carefully controlled. This problem is encountered in drilling from the earths surface, but is extremely aggravated when rotary drilling is attempted in sea, lake, and river bottoms from floating vessels. The drill string is, of course, supported from the floating vessel and is therefore moved up and down with periodic variations in the water level due to tidal and wave action as the interfering factor. The bottom of the hole, however, is fixed so that the point of suspension of the drill tubing effectively rises and falls. This prevents efiective weight control on the bit and has heretofore virtually precluded rotary drilling from floating vessels. The same problem interferes with most underwater operations conducted from floating vessels.

The present invention is therefore related to an improved method of suspension of mechanical equipment such as the drill tubing employed in rotary drilling operations and effectively solves the aforementioned problems, allows rotary drilling and other operations from floating vessels independently of wave and tidal action, and still permits accurate drill bit weight control and accurate positioning of any suspended object.

It is accordingly a primary object of this invention to provide an improved method for suspending objects from floating vessels in submarine or other underwater operations which overcomes tidal and wave action problems.

' It is a more specific primary object of this invention to provide an improved rotary drilling method which is conducted offshore or from any floating vessel.

Another object is to provide a process for rotary drilling of earth bores in which the hoist power employed to raise and lower the drill string is applied continuously during drilling through a fluid coupling which is capable of a wide variation in slip so as to provide a substantially constant torque and thereby provide a substantially constant lifting force on the drill string.

A further object of this invention is to provide a process for rotary drilling in which the hoist power transmitted to the top of the drill string is continuously applied to the draw works through a fluid coupling, capable of a controlled degree of slippage, in combination with the step of measuring in the conventional way the bit weight and modifying the torque in accordance therewith by varying the slip degree or the hoist engine power level to provide for a constant bit weight.

It is an additional specific object of this invention to employ the process defined by the foregoing objects in offshore rotary drilling to maintain bit weight in spite of water level fluctuations, as well as in other underwater hoisting procedures.

It is also an object of this invention to provide an improved apparatus capable of accomplishing the foregoing objects.

Other objects and advantages of the present invention will become more apparent to those skilled in the art as the description and illustration thereof proceed.

Briefly, the present invention comprises an improved process for hoisting in general, which is herein described and illustrated by the rotary drilling of earth bores. The illustrative process includes the steps of extending a drill pipe and bit downwardly through a well bore, turning the drill string so as to rotate the bit at the bottom of the hole to deepen it, and circulating down through the drill string and up through the hole a drilling fluid to cool the bit, support the borehole walls, and remove cuttings. in combination with these steps, the process of the present invention includes the improved step of applying the hoist power to the draw works continuously through a fluid power coupling so as to support a variable proportion of the weight of the drill pipe. Fluid couplings contemplated by the present invention are well known in the art and have heretofore been employed between the sources of power and the mud circulation pumps, the rotary table, and the like. They have also been employed intermittently in the transmission of power to the draw works for raising and lowering the drill pipe in order to overcome shocks of the applied load. They have not heretofore, however, been employed continuously during the drilling to transmit a continuous torque to the draw works as described in the present invention. These fluid couplings are commercially available from virtually every oil well and other heavy equipment supplier and are characterized by having a fluid coupling rather than a mechanical coupling between the input shaft connected to the power source and output shaft connected to the draw works or other load. Because of the fluid coupling there is no fixed speed relationship between the driven shaft connected to the load and the driving shaft connected to the engine. The degree of slip is variable depending upon the quantity of fluid present in the coupling between the driven and the loaded elements, the quantity of power supplied to the driving element, andthe degree of loading of the driven element, etc. One particular type of fluid coupling will deliver a substantially constant torque to the output shaft for a given engine power rate regardless of the load. When it is connected to the ordinary mechanical draw works it will provide a continuous force of constant value to the suspension point at the top of the drill string. This provides for the suspension of a constant proportion of the total drill string weight leaving a constant weight supplied to the bit. Another type of fluid coupling delivers a variable torque under these conditions and with these types the process of this invention includes the additional steps of measuring the weight on the bit and controlling either the fluid coupling or the power source to'pr'oduceithe' desired torque and supporting force and thus'leave unsupported the desired weight at the rotary bit.

The present inventionwith itscontinuous application of hoist force to the drill string during'drillin is applicable to regular inland rotary drilling in which the drilling platform is stationary, but'in which the'drill bit weight changes due to the deepening well bore; Constant control of drill bit weight is obtainedinspite of the continuous lowering of the-drill string; The former visual inspection of the weight gauge and manual variation of the draw shaft'brake are eliminated;

The presentinvention is applicable with fullest realization of its advantages :to offshore drilling and other operations from floating vessels which rise and fall periodically due to tidal andwave action. Herein, bit weight control is exceedingly. complicated by the rise and'fall of the drilling vessel. It has now been found that with the present invention employing a constant application of controlled hoist power during drilling through a fluid drive coupling, a complete elimination of the adverse elfects on bit weight due to tidal and wave action is obtained. The

vessel, therefore, can rise and fall as rapidly as about 20 times per minute and the weight on the drill bit at the bottom of the hole remains substantially constant. With a fixed power level maintained at the hoist engine and a fixed degree of slippage in the fluid coupling, a constant torque is applied through the fluid coupling and the draw works to provide a constant supporting or lifting force at the top of the drill string, leaving a constant downwardly acting force on the drill bit. As the vessel rises on a ground swell or with the tide, the added lift due to the rise in the drilling vessel would ordinarily raise the drill stem and support an additional amount of the total drill string weight decreasing the weight at the drill bit. The slippage in the fluid coupling through which hoisting power is transmitted continuously prevents the rise in the drilling vessel from lifting any additional proportion of the drill string weight and permits the payout of additional cable from the draw works through the crown and traveling blocks to the top of the drill string while maintaining the constant lifting force determined by the power level and the slippage. This maintains a constant predetermined weight on the bit in spite of the change in elevation of the drilling vessel. In the contrary situation where the vessel falls in level, the bit weight would ordinarily increase, relieving part of the lifting force. The excess torque, equivalent to the decreased lifting force now nec essary causes the draw works to draw in the excess line until an equilibrium tension is generated equivalent to the fixed torque applied to the draw works through the fluid coupling by the hoist engine. Thus, the same amount of drill ,string weight is supported by the constant application of power and, again, the drill bit weight stays constant.

In those situations where the fluid coupling is such that it does not ordinarily deliver a constant torque output with constant engine power and changing load, the con- 4.. flowing in the engine block ofthe internal combustion engines used as prime movers. Two other simple forms of cooling involve pumping the heated fluid through heat exchange means submerged in the surrounding water during, or through such means around which such water is pumped as through a cooling box on the floating vessel.

In the accompanying drawings which form a part of this application, Figure 1 schematically illustrates the general layout and assembly of the elements which areemployed in the process and apparatus of the invention, and Figure 2 schematically illustrates certain of those elements in greater detail.

Referring now to Figure 1, the apparatus there shown comprises a barge or like floating support structure 1 floating in a body of water 2 and held in a more or less fixe geographical position by means of anchors 3 and 30 attached to the barge by means of anchor lines 4 and 4. 1, respectively. A conventional drilling rig, comprising derrick 5, and rotary drill table 6 turned by means not shown, is supported on the deck of barge 1. Drill string 48 extends through drilling table 6 and the bottom of the barge, and terminates at its lower end in drill bit 7. The drill stem and drill bit are supported from travelling block 42,,

lines 44, and crown block 40, which is in turn connected to draw works 16 by means of fast line 38. Weight indicator 50, connected between lines 44 and a fixed point on the derrick or on the barge deck indicates the weight of. the. drilling string. Draw works 16 is driven by engine 10 operating through a fluid coupling device 14.

Referring now more particularly to Figure 2, engine 10 is supported on platform 12 together with fluid coupling 14 and'draw works 16. These elements are in turn mounted on a floating drilling vessel as shown in Figure 1. Engine 10 is provided with radiator 18, cooling fan- 20, exhaust line 22, and fuel inlet line 24 controlled by valve 26. A cooling system comprising pump 15, cooler 17, and valve 19 is provided to remove heat generated in fluid coupling" 14 due to the slippage. The main drive shaft indicated generally at 28 is connected to the driving element, not shown, of fluid coupling 14. Coupling 14 is provided with slippage or power transmission control 30. The driven element, not shown, of fluid coupling 14 is connected to output shaft 32 which in turn is connected to the input shaft 34 of draw works 16. The cable drum 36 of draw works 16 is connected to and turned by appropriate driving gears, not shown, but conventional in this type of apparatus. On cable drum 36 is wound fast'line ventional weight indicating instrument is connected to actuate, through a torque controller, either the power source or the degree of fluid coupling slippage so as to either change the power level or change the slippage when the vessel rises and falls. In this way, a constant bit weight is also maintained in spite of changes in elevation or level ofthe drilling vessel with nearly all of thefiuid power couplings. V

Heat due to the slippage is. generated in the fluid coupling and provision is made for dissipating it by circulating the heated fluid from the coupling through a cooler. This cooler may be a radiator, exposed to a new: of air similar to those'used in cooling the coolant 38 which extends upwardly to and over crown block 40 which is rigidly supported at the top of the drill derrick. Traveling block 42 is suspended'by two or more lines 44 terminating in a dead line 46 which runs from the crown block to an anchor point. In. inland drilling the anchor point is usually the bottom of the drilling tower and in offshore drilling this anchor point is located on the floating vessel; Suspended from the traveling block by means of the conventional hook and drilling fluid swivel is drill string 48. A conventional rotary table and kelly, not shown, are provided and used in connection with the process of this invention.

The torque delivered continuously through drive shafts 32 and 34 to draw works 16 during the drilling is controlled by the setting of valve 26 which regulates'the fuel into the engine and also by controller 30 which regulates the degree of slippage in fluid coupling 14. This torque. directly controls the tension in fast line'38 and, accordingly, the lifting force applied by the traveling block 42 at the top of drill string 48. As the supporting vessel tends to fall, tension in fast line 38 tends to be relieved permitting'the torque always applied to the draw works to reel in a length of fast line suflicient to maintain the original equilibrium tension in that line at a value suffi'-- stant and draw works 36 either pays out additional cable when the vessel rises or winds in additional cable when the vessel falls.

In order to eliminate any slight variations in bit weight caused by changes in delivered torque from the fluid coupling with motiton of the draw works, the conventional weight indicator 50 ordinarily attached to dead line 46 may also be connected to actuate controller 52 which in turn operates either fuel valve 26, when switch 54 is connected to terminal 56, or to actuate fluid coupling controller 30, when switch 54 is connected to terminal 58. The controller therefore regulates the prime mover either through alteration of the fuel supply or alteration of the fluid coupling to maintain a predetermined weight on the drill bit as indicated by weight indicator 50. In this way, a constant drill bit weight is maintained independently of the length of the drill string and of the position of the drilling platform with respect to the top of the drill string. Suitable controllers for these purposes are readily available. See for example the current catalog of the Fischer Governor Company of Marshalltown, Iowa, for example models 522 and 522T for lever-type controls and models 4100DSF with pilot valves for remote control.

The present invention was applied to inland drilling in the manner indicated in the drawing in drilling a well in a Southern California oil field. An 8-inch hole was drilled to the producing horizon at 3750 feet using a fluid coupling power take-ofl. from the prime mover constantly supplying power to the draw Works so that during rotation of the drill stem a predetermined proportion of the drill string weight was supported by means of a constant torque supply to the draw works through the fluid coupling rather than by anchoring or braking cable drum 36. The weight did not change appreciably during the time that drilling continued with a given number of stands of pipe in the string. Stands of drill pipe were added successively during progress of the drilling in the conventional manner with the drill string blocked in position in the hole and with the draw works power take-off adjusted to 100% slip. As drilling was continued with each added stand of drill pipe the fluid coupling was readjusted to a predetermined decreased degree of slip suflicient to support the desired fraction of the successively heavier drill string and leave the desired weight on the bit at all times during drilling.

The same process was applied in the drilling of a submarine core hole in the continental shelf off the coast of Southern California. In this area maximum tidal action accounts for a change in level of the floating drilling barge of about 8 feet. Wave action in the form of ground swells changed the level of the drilling barge by a variable amount depending upon the time of day and local weather conditions. The maximum change due to this action was 12 feet. Drilling was conducted through 225 feet of salt water and 27 feet of silt. Core samples were taken by means of a conventional core drill using the rotary drilling technique of this invention to a depth of 76 feet into the underlying rock. The derrick extended 65 feet above the deck of the drilling barge and the barge was anchored through radial spring lines to four anchors on the bottom, each located at distances of about 700 feet from the vessel. Substantially no lateral motion of the vessel occurred and the drill string was supported during drilling through constant application of hoist power through the fluid power take-01f from the prime mover. As the vessel rose and fell with wave action the draw works unwound and wound up cable from and to the fast line maintaining a predetermined tension therein which balanced the supplied torque from the fluid coupling. The rotary table rose and fell with each wave as it turned around the kelly and the weight indicator connected to the dead line showed substantially no change in drill bit weight during these fluctuations in level.

The present invention of conducting rotary drilling process including the step of supporting a substantial proportion of the weight of the drill string by means of a constant application of power through a fluid coupling to the draw Works has successfully eliminated disadvantageous changes in drill bit weight caused by changes in level of the drilling platform in offshore drilling and by changes in length of the drill string in inland drilling. The experimental operations in which this invention was employed appear to be successful in every aspect.

It should be understood that the weight and position control procedure and apparatus of this invention, which overcomes problems due to tidal and wave changes in water level, is applicable also to overcome these same problems in other underwater operations involving static hoisting. Some such operations include salvaging of sunken vessels and the like, raising any submerged object, laying submarine sewer and other pipelines, accurately placing rock and other materials in building and repairing jetties and breakwaters, preparing and building foundations and installing caissons for bridge and wharf supports, etc., from floating vessels. In these applications, the support cables are attached usually through a traveling block to a line running down into the water and attached to the object involved in the particular underwater operation and in which tidal and wave action ordinarily causes great interference.

A particular embodiment of the present invention has been hereinabove described in considerable detail by way of illustration. It should be understood that various other modifications and adaptations thereof may be made by those skilled in this particular art without departing from the spirit and scope of this invention as set forth in the appended claims.

I claim:

1. In a process for rotary drilling operations in areas of the earths crust submerged in water wherein a floating vessel subject to tide and wave motion is provided with rotary drilling equipment on the surface of the water over the drilling site, and drilling is conducted by rotating a drill pipe and bit extending through the water into the formation below, the improvement in said process which comprises: establishing a fluid coupling having its driving member connected to a prime mover and its driven member connected to draw works which support said drill pipe and bit, rotating said drill pipe and bit while the bit is in contact with said formation, rotating the driving member of the fluid coupling continuously in the direction which tends to lift said drill pipe and bit so as to exert a torque on the driven member, measuring the weight of said drill pipe and bit, and varying said torque in response thereto so as to apply a supporting force to said drill pipe and bit which is a predetermined amount less than the total weight of said drill pipe and bit, whereby said driven member assumes a rotational motion which is generally opposite to that of the driving member as the bit progresses through the formation, but said driven member also tends to rotate in both directions so as to maintain said supporting force substantially constant while said tide and wave motion changes the distance between said vessel and said bit.

2. A process according to claim 1 wherein said torque is varied by the step of varying the power level of the prime mover.

3. A process according to claim 1 wherein said torque is varied by the step of varying the degree of slippage in said fluid coupling.

4. A process according to claim 1 in combination with the step of cooling the fluid in said fluid coupling to dissipate heat generated therein during power transmission therethrough.

5. An offshore drilling structure comprising in combination, a floating vessel subject to displacement in the vertical plane; anchor means attached thereto for pre- V 7 V venting substantial displacement in the horizontal plane; rotary drilling means including a drilling table supported on said vessel, a drill string, and a drill bit; hoisting means supported on said vessel and supporting said drill string and drill bit, said hoisting means comprising a torque-producing prime mover, a draw works, and a fluid power coupling for applying said torque to said draw works; means for measuring the weight of said drill string and drill bit; and means for varying the torque applied to said draw works in response to said measured weight of said drill string and drill bit to maintain a constant unsupported weight of said drill string and drill pipe regardless of the vertical displacement of said vessel.

6. An apparatus according to claim 5 wherein said means for varying the torque applied to said draw works comprise means for adjusting the slippage in said fluid coupling.

7. An apparatus according to claim 5 where said means for varying the torque applied to said draw works comprise means for adjusting the power output of the prime mover. l

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